There’s a brand of nostalgia that puts your present self and the sum of your experiences back in the shoes of a younger, greener version. “If I only knew then what I know now” and so forth. Youth is wasted on the young, but even at your most naive, you knew more than you thought you did, and you were probably better at living in the present.
It's hard not to lock into what you think you already know, but also knowing that the information you are lacking is usually pretty easily obtainable.
Good thinking fuel.